Reinforcement, stabilization, replacement, reconstruction, or fusion of a joint or vertebrae may be indicated as a treatment of an afflicted region of a patient. Examples of specific treatments include spinal stabilization, spinal fusion, posterolateral spinal fusion, posterior lumbar interbody fusion, transforaminal lumbar interbody fusion, lateral interbody fusion, anterior lumbar interbody fusion, vertebral immobilization or reinforcement, intervertebral joint immobilization or reinforcement, degenerative disk stabilization, repair of traumatic fracture dislocation of the pelvis, treatment of degenerative arthritis, treatment of sacroiliitis (an inflammation or degenerative condition of the sacroiliac joint), osteitis condensans ilii, and treatments of other degenerative conditions of joints or vertebrae or other musculoskeletal injuries, diseases, conditions or disorders.
This reinforcement of intervertebral joints, sacroiliac joints, or other joint stabilizations may be accomplished by one or more existing methods, including inserting stabilizing implants such as support rods into the afflicted regions. Typically these fusion implants span an afflicted joint and may be anchored to bone tissue on either side of the afflicted joint using existing orthopedic fasteners such as pedicle screws or other orthopedic anchoring devices. These existing fusion implants may completely immobilize the afflicted joint or may allow limited or unconstrained movement to approximate or permit the normal movements of the afflicted joint.
One limitation of many existing fusion procedures involves the challenge of situating a fusion implant in suitably close alignment with the removed tissues of the patient to achieve a stable fixation of the joint or vertebrae. Existing implant structures may have insufficient engagement with the articular surfaces or cortical bone of the joint for adequate fixation or fusion. This failure to sufficiently stabilize and fuse the joint with the conventional implant structures and methods may result in a failure to relieve the condition being treated.
Another limitation of the fusion and fixation implants and associated anchors used in existing fusion procedures is the relatively large profile or prominence of the components. The large footprint of existing fusion implants and associated anchors necessitate the removal of considerable bone and/or soft tissue to prepare the area for the installation of the implant, possibly resulting in considerable post-operative pain. Further, the high profile or prominence of elements of the fusion or fixation implant projecting away from the spine or pelvis may chronically irritate the soft tissues, resulting in chronic pain during long-term use of the fusion implant and may require further surgeries and explantation.
Additional limitations of existing fusion implants are also related to the long-term use of the implants. Over time, the anchoring elements such as pedicle screws may loosen over time due to exposure to repeated loads associated with movements of the patient, thereby reducing the stabilization provided by the implant. Even if more robust anchoring devices or systems are used, the long-term use of these existing fusion implants are associated with an increased chance of injury to one or more joints adjacent to the reinforced joint.
The stabilization of afflicted lumbar intervertebral joints poses a particular challenge with respect to surgical interventions. The lumbar intervertebral joints are particularly vulnerable to injury or degradation because these joints bear the majority of the body's weight but also effectuate about half of the body's overall flexion movements (forward-backward bending). As a result, a sizeable fraction of back pain symptoms are associated with injuries or degradation of the lumbar intervertebral joints, in particular the L3-L4 and L4-L5 joints.
Treatment of spinal pathologies, including scoliosis, using existing lumbosacral fusion or fixation implants may increase the patient's risk of complications including loosening of anchor elements, implant-induced injury of surrounding joints, and/or implant-induced injury or chronic irritation of soft tissues surrounding the implant as described previously. Some existing lumbar fusion implants may provide additional anchoring to the ilium and/or sacrum bones of the pelvic girdle to enhance the robustness of anchoring and/or structural support. However, anchoring a lumbar fusion implant to one or more bones of the pelvic girdle presents additional risks of complications not yet completely addressed by existing implant systems or methods.
Due to the relatively dense concentrations of exposed nerves emerging from the sacrum region, the implantation of a transacrally fixed lumbar fusion implant is associated with an increased risk of nerve injury during implantation and/or chronic use of the implant. In addition, the bone tissue of the sacrum consists largely of lower density cancellous bone tissue, which is less structurally robust and therefore more vulnerable to anchor loosening relative to other bones. Lastly, the increased loading applied to the sacrum via the attached lumbar fusion implant may induce an accelerated degradation or failure of one or both sacroiliac joints.
Other existing lumbosacral fusion or fixation implants may provide additional anchors fixed to the ilium; the ilium contains a much higher proportion of higher-density cortical bone and therefore provides a more robust anchoring surface than the sacrum. However, additional loads induced by an ilium-fixed lumbar fusion implant may induce an accelerated degradation or failure of one or both sacroiliac joints. Although some existing lumbar fusion implants are anchored to both the ilium and the sacrum, alterations to the chronic loading of the articulating surfaces of the sacroiliac joints may induce accelerated degradation or failure of one or both sacroiliac joints.
In the practice of orthopedic and neurologic surgery, while attempting to correct a pathology of the spine by means of fixation or stabilization, strong forces can be concentrated on certain parts of the spine and pelvis. Specifically, the junction above or below a fixated or stabilized segment of the spine can undergo forces which can affect healthy alignment of the spine, or portions of the pelvis such as the sacroiliac joint. Unhealthy alignment of anatomic structures involved in such procedures can result in severe complications for example chronic severe pain, permanent disability and paralysis. The complexity of the spinal reconstruction, the sagittal balance realignment, the number of vertebrae involved, or other factors may increase the risk of complications. In published literature morbidity rates near fifty percent for such procedures. In order to minimize the forces a fixated or stabilized segment of vertebrae can create, a conventional technique employs the use of metal or plastic rods (or bands, cord, etc.) which can be configured to extend to a sacrum or ilium and screws inserted into either or both bones or across both bones which can then connect to the rods to help stabilize the spinal construct. Substantial problems with conventional techniques exist which can significantly affect a patient's recovery from the surgery.
A significant problem with certain conventional methods for pelvic fixation including the procedure mentioned above is that there is a tendency for the screws to pull out, loosen, break or otherwise cause complications due to the strong forces which can be present. Another significant problem with certain conventional methods for pelvic fixation including placement of a (S2 alar iliac (S2AI)) screw into the second sacral body (S2) which then crosses the sacroiliac joint (extra-articularly) and continues into the ilium extending across the cortical bone to better fixate the screw may be that the screw is positioned such that it violates the articular portion of the sacroiliac joint. Literature shows that this can occur up to 60% of the time. Due to the high chances of trauma caused by the screw extending to the articular portion of the joint, severe pain may result.
The inventive anchoring system for one or more elements of a spinal stabilization system described herein addresses the problems associated with conventional methods and apparatuses used to anchor one or more elements of a spinal stabilization system.